Effects of β-adrenoceptor agonists and antagonists on thyroid hormone secretion

Abstract

The effects of various β-adrenoceptor agents on radioiodine release from the thyroid were studied in mice pretreated with 125I and thyroxine. The non-selective β-andrenoceptor agonist isopropylnoradrenaline and the selective β 2-adrenoceptor agonist terbutaline both, and with the same efficacy, enhanced radioiodine release, whereas the selective β 1-adrenoceptor agonist prenalterol had no such effect. The non-selective β-adrenoceptor antagonist l-propranolol and the selective β 2-adrenoceptor antagonist ICI 118,551 both abolished the radioiodine release induced by isopropylnoradrenaline or by terbutaline. The selective β 1-adrenoceptor antagonist metoprolol inhibited the radioiodine response to isopropylnoradrenaline, but not that to terbutaline. Neither of the β-adrenoceptor antagonists influenced the radioiodine release induced by TSH. It is concluded that the β-adrenoceptors involved in the regulation of thyroid hormone secretion are mainly of the β 2-subtype, and, further, that β-adrenoceptor agonists and TSH exert their thyroid hormone secretory effects through different mechanisms.